Biogeography, Species Richness, and Island Biogeography

Flashcards defining key vocabulary, foundational concepts, and experimental studies in biogeography, species diversity gradients, and the equilibrium theory of island biogeography.

Biogeography

The study of the geographic distribution of living organisms and the underlying reasons for where species are found.

Alfred Russel Wallace

The ecologist known as the father of biogeography, who also independently formulated the theory of evolution by natural selection alongside Charles Darwin.

Latitudinal Diversity Gradient

The broad ecological pattern characterized by higher species richness and diversity near the Equator and progressively lower diversity toward polar latitudes.

Seabirds

A taxonomic group that presents an exception to the latitudinal diversity gradient by showing higher species diversity at temperate and polar latitudes than in the tropics, driven by marine productivity.

Speciation

The evolutionary process resulting in the creation of new species, typically driven by natural selection.

Extinction

The natural process where species die out completely because they fail to acquire the random mutations needed to adapt to changing environmental conditions.

Dispersal

The ecological mechanism by which organisms move from one geographic location and establish themselves in a new area.

Species Diversification

The net increase or decrease of species within an ecosystem, calculated as speciation rate minus extinction rate when dispersal rates are assumed to be steady.

Species Diversification Rate Hypothesis

An explanation for tropical diversity proposing that stable temperatures and large land areas decrease extinction rates while narrow ecological niches promote geographic isolation and rapid speciation.

Climatic Time Hypothesis

An explanation for tropical diversity stating that the tropics have remained climatically stable for longer periods (unaffected by events such as ice ages approximately $10,000$ years ago), granting species more uninterrupted time to evolve.

Productivity Hypothesis

An explanation for the latitudinal diversity gradient proposing that higher direct solar radiation at the Equator produces greater primary productivity, supporting larger populations and higher carrying capacities.

Species-Area Curve

A mathematical relationship and plot showing species richness as a function of geographic area, often log-transformed to produce a linear regression.

Island Species-Area Slope

A steeper slope on a species-area graph compared to mainland systems, indicating that species richness accumulates much more rapidly per unit of added land area.

Endemic

A term describing a species that is naturally restricted to a single, localized geographic area, such as a desert pupfish living exclusively in one isolated spring.

Equilibrium Theory of Island Biogeography

A foundational ecological theory formulated by Robert MacArthur and E. O. Wilson stating that the species richness of an isolated habitat reaches an equilibrium governed by rates of immigration and extinction.

Distance Effect

A principle of island biogeography stating that islands located closer to the mainland have higher immigration rates than islands situated far away.

Area Effect

A principle of island biogeography stating that larger islands support larger populations and greater resources, leading to lower extinction rates compared to smaller islands.

Habitat Island

Any patch of isolated habitat surrounded by an inhospitable or dissimilar matrix, such as mountaintops, desert springs, or forest fragments within suburban development.

Mangrove Fumigation Experiment

An experimental field study conducted by E. O. Wilson where small mangrove islands were enclosed and fumigated to exterminate all fauna, monitoring recolonization to empirically test island biogeography theory.

Gamma Diversity

The total regional species richness or overall regional pool of species present across a broad geographic scale.

Beta Diversity

The measure of diversity that reflects the turnover or comparative difference in species composition between local sites or between local communities and the regional species pool.

Biological Dynamics of Forest Fragments Project

A long-term ecological study in the Amazon rainforest that examined the impacts of habitat fragmentation by assessing species retention within experimental forest patches surrounded by cattle pastures.